Apparatus for the electrical production of light.



P. c. HEWITT; APPARATUS FOR. THE ELECTRICAL PRODUCTION OF LIGHT.

APPLICATION FILED APB.11, 189B. 1 ()3'Q 178 Patented June 18,-1912.

WITNESSES:

@. /9.7l1m"l- I I I 1 I UNITED STATES "PAT NT. OFFICE.

PETER COOPER HEWITT, OF NEW YORK, Y., ASSIGNOR TO COOPER HEWITT ELECTRICCOMPANY, A. CORPORATION OF NEW YORK.

APPARATUS roa m ELECTRICAL rnonuo'rron or LIGHT.

A man filed April 11, iaaa. Serial No. 677,199.

To all whom it may comma Be it knownthat 1, PETER COOPER HEW- n'r, ofthe city of, New-York, boro h of Manhattan, in the county and State-oNew York, have invented certain new and useful Improvements in A paratusfor the Electrical Production of lght, of which the following is a full,clear, and exact description.

new and useful means of roducing light by electricity, whereby a; lightof high illuml nating power isproduced', and the intensity and color ofthe light may be varied. V

I have discovered that certain vvapors of specific density and physicalcondition have the propertyof becoming intensely hght radiant when anelectric. current is passed I through them. Such a vapor-is the vapor ofmercury, sodium, iodin and other metals, gecuhar epends each producing alight with colors to itself. The light givinglquality chiefly on thedensity of t e vapor, as well as the material, it being most intense atthe point of saturation, or boiling paint of the metal, the light givingquality somewhat proportioned to the density. esides simple metallicvapors, other gases have this propertyto acertain extent, but most ofthem are objectionable on account of the temperature necessary, and alsoon account of the electrical resistance at the point where their vaporis in the physical state,

which allows them to be light radiant. For

these reasons their use in many cases is impracticable. In the case ofmercury, which 1s a fair exampIe of a metal volatihzlng at a practicaltemperature, the vapor is inclosed or formed in atube whose ends areturned 6 down so as to .hold a globule of mercury,

into which are led wires for conducting the electrical current, whichwires may be submerged in the volatizable materialor not, as desired. Incase the wire or electrode projects through the .material to bevolatilized $5 the becomes heated on the discharge o 59 not snflicientlyfull of vapor.

tin-electric current, which in turn heats the material to be volatilizedandvolatihzes 1t,

an" the this w th-seam; it the tube is.

-.not'a ready o'f such a temperature that it is It is ,well known thata' .wire leading into an-attenuated atmosphere becomes heated, althoughthe same sized wine will conduct the circuit under ordinary conditionswithout heatlnig. In the? case where the material to be volat Theobjectof my inventioniis to provide a ized constitutes the electrode, thecurrent .heats the electrode direct, producing the same effect. A .tubemay be-constructed contalnmg an exact amount of vapor (or materialtoproduce the vapor) necessary to roduce this intense light.electrically, in w ich case the exact degree of vapor density andSpecification e: I -etters Patent. P t t u 1912.

physical condition can be produced which is I most advantageous. Theelectrodes must be made of such size-as not to be deteriorated by theelectrical'disch'arge. The light actlon of these tubes is intermittentand the electric current impulses or oscillations can be made withthefrequency desired, and so rapid as to require a .most delicateinstrument to detect that the light is not continuous. A tube in theform described, one quarter of an inch in diameter,-one foot in lengthwill produce a light too brilliant to look at, the light beingmore thanahundred candle power. The quantity of light may be varied by the currentused, from great brilliancy to the bare luminosity of ordinary vacuumtubes or Geisler tubes. This tube is practically indestructible, havingnothing to ruin or destroy, operating at somewhere about a temperatureof 300 C., if mercury is used. In the case where other metals ormaterials are used, my tubes operate at the temperature a little abovethe point or thereabout, of thesubstance in a vacuum. It ,is advisableto use a substance which volatilizes at ordinary temperatures as near aspossible, for economy. The metal'rubidium gives a deeper red light thanany other, and I prefer to use this metal or a metal having a deep redband in the spectrum, or a proportion of this metal to obtain a deeperred color in my tubes. Potassium, also 'thium give fair results, thetemperatures being higher. In practice a more agreeable light will beproduced by the judicious use of two or more tubes, each containingdifierent vapors.

In orderto more fully explain my invention, reference is had.to theaccompanying drawing forming a part of the specification, in whichsimilar charactersof reference indicate corresponding parts in all thefigures.

Figure 1 is a side elevation of one formof a plant for producing light;Fi 2 is a side elevation of a modified form 0 tube; and Fig. 3 is alongitudinal section of a straight tube having a volatilizable material.at one end only.

A is an electric generator, B is a transformer, C a condenser, D D"wires, terminat ng in the electrodes E E, extending into thevolatilizable substance F, contained in the bulbs G G of the vacuum tubeG. e

The form of converter shown in Figs. 1 and 2 is shaped and arranged likean inverted letter U. The two legs of the U are shown similar andsymmetrical,.as are also the electrode chambers, the bodies of liquidtherein and the leading-in wires. From this symmetrical arrangement itresults that when an alternating electromotive force is impressed firston one electrode and then on the other as by the transformer B, or bycondenser C, or by both together, the fluxes in both directions, findsubstantially the same physical and electrical conditions at theirrespective electrodes and the operations and reactions are the same foreach half wave except that the directions are re versed. v

To operate my light, I use an electric current of varying voltage,having found that from 500 to 5,000 volts most successful, but it can beoperated at many other electrical pressures, depending. on "the lengthof the tube G desired to operate, and the quantity of light to beproduced; also for the material used. Iplace across the wires D D lead-'ing to the tube G the condenser Cwhich is of suitable capacity; theobject of the con denser being to accumulate the electric current duringthe minute period of time when the current is notpassing through thetube G, and deliver the accumulation to the tube G during the time thetube is taking current. The condenser also aids the light giving qualityof the tube. This condenser C-being in resonance with the tube Gand-with the source of current, will adjust the voltage of thee urrentin some degree to any varying resistance that may occur in the tube. Thetube itself is a condenser of certain capacity under the condition thatI establish, and under light giving conditions is oscillatory orintermittent, acting somewhat as a dis-' charge for the condenser,producing waves or pulsations in the current from the condenser. Thetube G is constructed with the volatile electrodes E E in the bulbs G, GG G and is proportioned in size to the current to be used. Theresistance of the vapor in a high degree of attenuation is greater thanit is when it becomes a little more dense; then becoming more dense theelectrical resistance increases so that if the electrodes overheat, thevapor generated will shut off the electric current imtil they are againsufiici'ently cool, but with a properly constructed tube the volatilizedmercury will condense atsubstantially the same rate at which it isvolatilized, so that the shutting olf of the current dces not occurexcept through accident and in any g1ven' case may obviously beprevented by any means which will decrease the rate of evaporation orincrease the. rate of condensation. 'At a conpor to flow through thetube, or generate in the tube and flow into the pump until it hascarried away with it all the impurities existing in the tube. When thisis accomplished at .the required vapor density (pressure andtemperature), the fact becomes self-evident by the great quantity oflight coming from the tube. The quantity of light is approximatelyproportional to the vapor density. The quantity' of light is underabsolute control, electrically or otherwise. I have found it--ad\-'antageous, even when operating tubes at almost atmosphericpressure temperature. to prevent radiation of heat to avoid the heatloss. As the vaper in the tube is very attenuated in the case of metalsthat volatilize above the atmospheric temperature, it may becomenecessary in the economical use of some of them to use a starting deviceto acquire the proper vapordensity on starting.*- Such a starting devicemay consist of applied or external heat or an increased electricalpotential for the time beings: I'have found in the case of mercury wherethe tube operates at about 300 C. that by' supplying from an outsidesource, the heat which otherwise would be radiated-from the tube, I havea somewhat -correspondingincreased production of light.

Infact, with the tube operating at this temperature, which tube maybe ofthe dimensions-set forth in the early part of the specification, abrilliant light of especially high efliciency may be secured, evenwithout the supplyin of heat from an outside source. These tu es may bemade in almost any shape from spirals to straight tubes, or invertedU-shaped tubes, or U-shaped tubes; but'in the case of a U-shaped tubeused for volatile material I prefer to use the invert-. ed U-shapedtube, shown in Figs. 1 and 2, but in some cases the tube may be used orformed with a downwardly curved intermediate portion containing a bodyof mercury which may fill the cross-section of the tube, so as to form apartition separating two vacuous spaces, or I may use two tubes jointedtogether and having a body of mercury at the point of juncture. In orderto equalize the pressure within the tube, I may provide the same with areservoir Gr in communication with the interior of the tube to be filledwith vapor, which, however, is not affected by the current nor renderedluminous, as the current does not pass through it, and hence the vaporcontained therein can act as an equalizer to give the each end intoenlargements,

In producing my tubes containing mor cury I have found that a very-smallamount of oxygen or oxid of mercury in the tube increases in a markeddegree the electrical resistance and impairs the light radiatingquality. I have also found that the combination of two or more tubes,each giving rays of light of a different color, is advantageous.

I claim as my invent-ion:

l. A mercury vapor lamp comprising an inverted U shaped exhaustedcontainer with an enlargementat each end partly filled with mercuryconstituting electrodes.

2. A mercury vapor lamp comprising an inverted U shaped exhaustedcontainer with an enlargement at each end partly filled.

with mercury, and also provided with a regulating chamber communicatingwith the interior of the main chamber cut out of th path of the currenttherein.

3. A vapor electric lamp having a highly exhausted chamber formed in theshape of an inverted. U, havinga main light giving portion of uniformdiameter expanded at said enlargements beingepartly-fi led with mercurycon stituting'electrodes and a condensing chamber centrally locatedalong said tubular portion whereby the vapor pressure within thecontainer is re lated.

4. The combmation with a mercury vapor lamp including ahighl exhaustedcontainer having a curved tubu ar light giving por tion, twoenlargements ofsaid tubular portions located at ldwer extremities insaid container, and mercury electrodes at the extremities of saidtubular portion, together with an electricsource therefor adjusted tomaintain a .temperature of approximately 300 degrees centigrade insaid-tube whereby an eflicient source of illumination is secured.

5. A mercury vapor apparatus comprising an exhausted container, suitablemercury electrodes therein and a light giving tubular portion thereoftogether with means for adjusting the density of the mercury vaportherein during normal operation to the density corresponding toapproximately 300 degrees centigrade, said means consisting of bulbsterminating said tubular portion whereby additional condensing surface,is

obtained for said vapor.

6. A mercury vapor apparatus comprising i an exhausted container,suitable mercury electrodes therein and a light giving tubular ortionthereof, together with means for adusting the density of the mercuryvapor therein during normal operation to the density corresponding toapproximately 300 degrees centigrade.

.7. A mercury .vapor apparatus comprising an'exhausted container,separated bodies of mercury therein operating as electrodes and a lightgivin portion of said container between said e ectrodes,'together withmeans for adjusting the density of the mercury vaporin sai containerduring normal operation to the density corresponding to 300 degreescentigrade approximately, said means consistingof portions of saidcontainer exposed to themercury vapor outside said light giving portion,whereby said adjustment of the mercury vapor density is obtained.

PETER COOPER HEWITT. Witnesses:

EVERARD BOLTON MARSHALL, GEO. M. HOPKINS.

